The invention relates to a composite structure, and a method of making same.
Composites are known to include a first nonmetallic component and a second component made either of a metal or a nonmetal, with the first and second components being joined together by a bonding material. Typically, the bonding material is a glue which migrates between the individual components during the bonding process. The bond strength, however, achieved in this manner is too weak for many applications, especially at elevated temperatures. In addition, heat transfer through the glue layer is poor, and the thermal expansion coefficient is much higher compared to metal and nonmetals, e.g. ceramics. It has thus been proposed to utilize soldering to effect a much better bond quality.
Ceramic surfaces which are to be soldered with metal, however, have to be pre-treated, i.e. metallized, with the metallizing step requiring high firing temperatures. If so-called active solders are employed, metallization of the ceramic surface may be omitted, but the actual soldering process is in this case rather complex.
Consequently, soldering is more complicated than gluing, and yet frequently produces only poor results as far as bonding strength is concerned.
Another bonding method involves direct copper bonding (DCB). This process, however, is only suitable for attaching copper to ceramic material.